naginterfaces.library.blast.dwaxpby

naginterfaces.library.blast.dwaxpby(alpha, x, beta, y)

dwaxpby computes the sum of two scaled vectors, preserving input, for real scalars and vectors.

For full information please refer to the NAG Library document for f16eh

https://support.nag.com/numeric/nl/nagdoc_30/flhtml/f16/f16ehf.html

Parameters

alphafloat

The scalar $\alpha$.

xfloat, array-like, shape $\left(n\right)$

The $n$-element vector $x$.

If $\text{incx}<0$, $x_{\text{i}}$ must be stored in $x[(n-\text{i})\times \left|\text{incx}\right|]$, for $\text{i}=1,2,\dots ,n$.

If $n=0$, $x$ is not referenced.

betafloat

The scalar $\beta$.

yfloat, array-like, shape $\left(n\right)$

The $n$-element vector $y$.

If $\text{incy}>0$, $y_{\text{i}}$ must be stored in $y[(\text{i}-1)\times \text{incy}]$, for $\text{i}=1,2,\dots ,n$.

If $\text{incy}<0$, $y_{\text{i}}$ must be stored in $y[(n-\text{i})\times \left|\text{incy}\right|]$, for $\text{i}=1,2,\dots ,n$.

Intermediate elements of $y$ are not referenced.

If $\beta =0.0$ or $n=0$, $y$ is not referenced.

Returns

wfloat, ndarray, shape $\left(n\right)$

The elements $w_i$ of the vector $w$ will be stored in $w$ as follows.

If $\text{incw}>0$, $w_i$ is in $w[(\text{i}-1)\times \text{incw}]$, for $\text{i}=1,2,\dots ,n$.

If $\text{incw}<0$, $w_i$ is in $w[(n-\text{i})\times \left|\text{incw}\right|]$, for $\text{i}=1,2,\dots ,n$.

Intermediate elements of $w$ are not referenced.

Raises

NagValueError

(errno $-4$)

On entry, error in parameter $\text{incx}$.

Constraint: $\text{incx}\ne 0$.

(errno $-7$)

On entry, error in parameter $\text{incy}$.

Constraint: $\text{incy}\ne 0$.

(errno $-9$)

On entry, error in parameter $\text{incw}$.

Constraint: $\text{incw}\ne 0$.

Notes

dwaxpby performs the operation

$$w\leftarrow \alpha x+\beta y\text{,}$$

where $x$ and $y$ are $n$-element real vectors, and $\alpha$ and $\beta$ are real scalars.

References

Basic Linear Algebra Subprograms Technical (BLAST) Forum, 2001, Basic Linear Algebra Subprograms Technical (BLAST) Forum Standard, University of Tennessee, Knoxville, Tennessee, https://www.netlib.org/blas/blast-forum/blas-report.pdf